Week 02
Revision day
No new topic today. Marks in an OA are lost to the same few mistakes, so spend the day on yours: finish what is still open in both tests, then reread the common mistakes of every topic.
Day 7 · Week 1 test
Retake the Week 1 test
0 of 12 solved. Open the set once more and time yourself on the hard ones.
Day 13 · Final test
Retake the final test
0 of 12 solved. Open the set once more and time yourself on the hard ones.
Every topic
Reread the common mistakes
One short list per topic. Each link opens the topic at that list.
- Day 1SELECT, WHERE, ORDER BY & LIMIT
- Day 2Aggregation, GROUP BY & HAVING
- Day 3CASE WHEN, Conditional Aggregation & Pivots
- Day 4INNER & LEFT JOIN: Combining Tables
- Day 5Self Joins, Anti-Joins & Existence Checks
- Day 6Subqueries, CTEs & Set Operations
- Day 8Window Functions I: ROW_NUMBER, RANK & Top-N per Group
- Day 9Window Functions II: LAG/LEAD, Running Totals & Gaps
- Day 10String & Date Functions
- Day 11Hard Company Problems: Combining Everything